Xin câu trả lời hay nhất ạ!
Program abcde;
Uses crt;
Var n,i,S:integer;
begin
clrscr;
write('Nhap n: '); readln(n);
S:=0;
for i:=1 to n do
if (i mod 3=0) and (i mod 6<>0) then S:=S+i;
write('Tong cac so chia het cho 3 ma khong chia het cho 6 la: ',S);
readln
end.